This invention relates to efficacious antiperspirant characterized by a property that renders invisible or transparent residue which remains on the skin. More particularly, the invention provides a highly efficacious concentrated antiperspirant system which when formulated into a conventional antiperspirant formulation and applied to the skin does not give unsightly white residue on the skin and clothing. The reduced residue effect of the antiperspirant product may be in the form of a stick, soft solid, suspension, roll-ons or spray, etc. The reduced residue or low residue means the product on application to the skin provides no discernible whiteness or visible residue.
The antiperspirant and deodorant market offers a wide diversity of products. The physical forms of antiperspirants vary greatly. They include aerosols, pump sprays, squeeze sprays, creams, roll-ons, suspension roll-ons, deodorant sticks, clear gels, soft solids, etc. First and foremost in the hierarchy of consumer needs is long lasting control of odor and wetness. Consumers also want their antiperspirants to have excellent sensory properties on application and certain aesthetics. The preferred form of antiperspirant in USA is the stick application due to their high efficacy and good application properties.
Antiperspirants (except aerosols and sprays) are applied to an area of the body such as the axilla by rubbing to deposit a layer of antiperspirant. Accordingly, it is desirable that the ingredients used in any antiperspirant formulation result in an antiperspirant which is smooth, non-greasy, feel warm, quick drying, non tacky and leaves no visible residue. One of the disadvantages that exist with many stick formulations is that a white chalky residue is often left on the body and transferred to clothing. Since the use of dark-colored garments has increased among consumers, women in particular are dissatisfied with white residue from personal care products including antiperspirant and deodorant on clothing. A chalky residue after use of an antiperspirant stick is due in part to the fact that relatively large particles of the antiperspirant salt are employed in stick antiperspirants. Since the antiperspirant stick is white the deposit on the skin is also white.
In the early 1990""s, clear products swept the consumer market place bringing everything from transparent dishwashing liquid to colorless colas. Although the popularity of these products has faded in some segments, product clarity remains a market force in the personal care industry. No where is a transparent product more sought after than in the antiperspirant stick market where consumers associate clarity with the lack of unsightly white residue on skin and clothing. This desire has prompted manufacturers of antiperspirant and deodorants to develop clear products. There are several apparent benefits associated with clear antiperspirant products. A clear product conveys a clean, pure and natural image; i.e., in an antiperspirant no visible product residue is left on skin or clothing. Consumer research rates clear products high on perception of superiority. The technology associated with clear stick and clear gel is specific and restricts the type of an antiperspirant active that can be used. Some of the important requirements for each of various antiperspirant forms are described below:
With respect to Clear Stick Antiperspirants:
The antiperspirant active must be stable in soluble and transparent form in the solvent system used; the solvent can be the same as that used to form the basic matrix for the gelling agent, or an alternative solvent.
An antiperspirant active that has already been pre-solubilised in a polyhydric alcohol, such as propylene glycol. This pre-solubilization ensures the formation of crystal clear compositions even in mixed glycol systems.
Use of enhanced efficacy aluminum zirconium actives is preferred to improve efficacy since the levels of use of the antiperspirant actives in clear sticks are markedly lower than in conventional solids. The comparative values are about 10-15% active level in clear sticks versus about 20-25% active level in opaque or translucent antiperspirant sticks.
Use of buffers to stabilize Di-benzaldehyde Monosorbitol Acetate (DBMSA) gelling agent or self buffered actives with higher pH than conventional antiperspirant actives.
The potential disadvantages with clear antiperspirant sticks include:
These products exhibit different application properties, particularly some stickiness after application and a less dry feel on the skin.
There is a potential for greater skin irritation due to the relatively high levels of glycolic fluids currently employed.
Clarity depends on the implementation and control of very precise manufacturing procedures at relatively high process temperatures and pHs. Also, antiperspirant salts themselves are weak oxidising agents, and under certain processing conditions may cause some degradation of glycols.
Shelf life stability frequently becomes difficult with clear sticks, and when they are unstable it becomes especially evident to the consumer. Unlike opaque products, clear sticks that begin to separate or cloud constitute a distinct and immediate turn-off for the consumer.
Lower clinical efficacy is generally acknowledged for this form of product, although they do conform to the Monograph requirement of a 20% sweat reduction in at least 50% of the test subjects. Lower efficacy is attributed to lower concentration of the active and higher pH of the active.
With respect to Clear Gel Antiperspirants:
Clear gel antiperspirant products offer several advantages. To illustrate, there is no product residue during or after application and a water-white clarity is achievable. High levels of enhanced efficacy actives can be used to deliver the expected levels of wetness protection. This is also a decided advantage compared to clear stick products.
There are several possible approaches to develop transparent formulations, such as the formation of gelled or thickened solutions, or the formation of micro-emulsions containing relatively high surfactant concentrations. Both of these approaches possess ingredient and production limitations.
A relatively simple and versatile third option is to form a water-in-oil emulsion in which the refractive indices of the continuous and dispersed phases are matched. This requires a precise control of the refractive index. The addition of a silicone surfactant such as dimethicone copolyol is desirable to achieve stability. Many formulations use a pre-blended combination of volatile silicone and dimethicone copolyol, also known as xe2x80x98self-emulsifying volatile siliconexe2x80x99, for ease of formulation.
Technically speaking, these emulsions are not microemulsions. The continuous or oil phase is typically a blend of liquids, and can include, for example, additives, such as, cyclomethicone, dimethicone, mineral oils, and various esters, as well as the silicone emulsifier.
The disperse or water phase typically includes one, or a combination of various polar species such as water, propylene glycol, sorbitol, glycerin, and ethanol, as well as the antiperspirant active.
To provide an optically clear gel, the refractive indices of the oil and water phase are adjusted as necessary to bring them within 0.0004 to 0.001 units at room temperature. Thus, the precise control of refractive index of an active and both the continuous and disperse phases is extremely important for this technology. Drawbacks to clear gels are that they suffer from becoming hazy when temperature changes or due to the evaporation of volatile ingredients like alcohol/silicone, causes an imbalance in the formulation. Efficacy of clear gel is also not as high as for opaque sticks and soft solids.
Reduced Residue Sticks
A solution to the consumer demand for an efficacious product with no residue is an opaque white stick with reduced residue or no residue. A number of patents have been issued for reduced residue sticks. However, there is a need for an active which when formulated into a solid gives no visible residue, has high efficacy, has silky feeling, has no tackiness and dries rapidly.
To achieve this objective two different approaches were investigated. Common to both approaches was the incorporation of an activated antiperspirant to improve efficacy whose refractive index has been modified by forming an adduct with a suitable organic solvent. The approach involved making a dense spherical particle to minimize surface area per unit mass while maintaining aesthetically acceptable application making use of sphericity of particles. The second approach was to reduce average particle size to about 1 micron, and further reduce refractive index of the active by enrobing it with a selected organic fluid which is dermatologically acceptable for topical application and facilitate particle size reduction during comminution.
The steps involved in preparing the novel composition of the invention comprise:
Preparing an inorganic-organic adduct of activated or nonactivated basic aluminum chlorides and comprise those having the formula
Al2(OH)6xe2x88x92x1Yx1(R)pxe2x80x83xe2x80x83(1)
wherein Y is Cl, Br, I and/or NO3 and x1 is greater than zero and less than or equal to six (i.e., 0 less than x1xe2x89xa66); wherein xe2x80x9cRxe2x80x9d is an organic solvent having at least two carbon atoms and at least one hydroxy group and xe2x80x9cpxe2x80x9d has a value of from zero to 1.5;
and including reaction products of those of the above formula and zirconium compounds of the formula
ZrO(OH)2xe2x88x92abXbxe2x80x83xe2x80x83(2)
wherein X is a member selected from the group consisting of halide, nitrate, perchlorate, carbonate or sulfate; b varies from 0.5 to 2; a is the valence of X; (2xe2x88x92ab) is greater than or equal to zero.
A particular group of such antiperspirant active includes various aluminum-zirconium-glycine salts with the formula:
AlnZr(OH)(3n+4xe2x88x92x)Yx(AA)q(R)pxe2x80x83xe2x80x83(3)
wherein xe2x80x9cnxe2x80x9d is about from 2.0 to 10.0; preferably from 3 to 8;
wherein xe2x80x9cxxe2x80x9d is from 1.4 to 12.3, calculated from metal to chloride ratio (M/Cl, 0.9:1-2.1:1); preferably from 2 to 8, wherein xe2x80x9cYxe2x80x9d is Cl, Br, I and/or NO3;
wherein AA is an amino acid, and xe2x80x9cqxe2x80x9d is from about 0.5 to 3.0, preferably from 1 to 2; and
wherein xe2x80x9cRxe2x80x9d is an organic solvent having at least two carbon atoms and at least one hydroxy group and xe2x80x9cpxe2x80x9d has a value of from zero to 1.5; and
aluminum or aluminum and zirconium complexes having metals/anion ratio of 0.9:1 to 2.1:1 where an anion could be Cl, Br, I and/or NO3, with or without additives such as amino acids or polyhydric alcohols or combination thereof.
The invention contemplates also those antiperspirant actives comprising aluminum and aluminum zirconium salts combined with zinc and/or tin, i.e. Al/Zr/Zn, Al/Zn, Al/Sn, Al/Zr/Sn, and the like, actives.
The organic solvent which may be employed in preparing antiperspirant formulation of the invention may be selected from any of the suitable polyhydric alcohols, non-polyhydric alcohols and other suitable organic solvents which are generally used in cosmetic compositions and which are liquid at room temperature and preferably have refractive index (RI) less than 1.5. Thus, some organic solvents used in preparing adducts of basic aluminum chloride are propylene glycol (PG) RI 1.430, dipropylene glycol (DPG) RI 1.446, tripropylene glycol (TPG) RI 1.454, 2 methoxy ethanol RI 1.402, 1-methyl 2-propanol RI 1.403, 2 ethoxy ethanol RI 1.407, and 3 methoxy butanol RI 1.411 and silicone copolyols.
The process technology used for the preparation of an antiperspirant adduct comprise of mixing basic aluminum chloride as represented by the general formula.
Al2(OH)6xe2x88x92x1Yx1
wherein Y is Cl, Br, I and/or NO3 and x1 is greater than zero and less than or equal to six (i.e. 0 less than x1xe2x89xa66) is mixed with a suitable organic solvent such as propylene glycol, dipropylene glycol, tripropylene glycol or glycerin or a combination thereby at room temperature to about 105xc2x0 C., may be refluxed for 30 minutes to about 4 hrs; is cooled to room temperature is either dried or mixed with zirconium hydroxy chloride glycinate solution having Cl/Zr atomic ratio of (0.8:1 to 2:1) and which has been refluxed for 2 hrs. The resultant solution is allowed to react at least for 30 minutes and is then filtered to obtain slightly amber to colorless solution. This solution is then dried by suitable conventional means (viz spray dryer, vacuum dryer, oven dryer, tray dryer, freeze dryer, etc.) to yield a homogeneous composition with the modified refractive index. The change in RI is a function of the organic solvent chosen, concentration of the solvent in the final product and drying method used and the amount of water associated with the adduct.
Organic solvent may be added to zirconium hydroxy glycinate solution before, during or after the refluxing step or it may be added after zirconium hydroxy glycinate solution has been added to basic aluminum chloride and just before the spray drying at room temperature or at temperature up to 100xc2x0 C. Alternatively some of the organic solvent may be added to basic aluminum chloride and the remainder to zirconium hydroxy glycinate solution.
Refractive index of various basic aluminum chloride adducts and of aluminum zirconium glycine propylene glycol complex prepared in Reheis lab are shown in Table I.
The data in Table I show significant reduction in RI of aluminum zirconium tetrachlorohydrex glycine propylene glycol complex. The procedures described in U.S. Pat. Nos. 3,420,932; 3,405,153; 3,472,929; 7,507,896; 3,523,130; 3,555,146; 3,792,070 may be used alone or in combination with the technology used in U.S. Pat. No. 5,718,876 to form antiperspirant adducts in accordance with the present invention and as described in the present application. The relevant disclosure in these patents is incorporated herein by reference.
Various experiments were conducted to study the effect of metals to chloride ratio, the amount of bound water associated with the product, degree of polymerization, concentration of organic solvent in adducts and drying methods viz vacuum oven drying, freeze drying and spray drying. Basic aluminum chloride antiperspirant showed change in refractive index by xc2x10.01 to xc2x10.02. However, higher change in RI of Al/Zr complex was seen when an adduct was formed with an organic solvent such as propylene glycol and spray dried using the approach described in U.S. Pat. Nos. 4,089,120 and 4,147,766.
The Effect of Surface Area/Unit Mass on the Antiperspirant Actives
The advantage offered by the patented spray drying technology described in U.S. Pat. No. 4,089,120 is that perfectly spherical thick walled particles with high bulk density and a very narrow particle size distribution is obtained. Table II shows comparison of physical properties of regularly spray dried aluminum zirconium tetrachlorohydrex powder and micronized to superultrafine grade which is used almost universally in the manufacturing of efficacious suspensoid stick and macrospherical aluminum zirconium glycine propylene glycol tetrachlorohydrex complex. The reduced surface area per unit mass results into reduced number of particles/mass and results into less visible white residue.
The Hygroscopicity of Antiperspirant Actives
Since activated products tend to be more hygroscopic they have significantly lower critical humidity (equilibrium moisture) values than their corresponding unactivated form and they pick up moisture readily under ambient conditions. Thus, an activated salt""s RI is lowered upon application more readily than of an unactivated salt and show less white residue.
Complexing an antiperspirant active with propylene glycol not only tends to lower the refractive index but also lowers critical humidity and makes the product very hygroscopic. (Equilibrium moisture was determined using the method described in a paper titled xe2x80x9cEquilibrium Moisture Content of Antiperspirant Systemxe2x80x9d published in Aerosol Age December 1974). This is highly beneficial as it further lowers RI upon application and thereby reduces visibility of the residue. The reduction in critical humidity or increase in hygroscopicity as the antiperspirant active is activated and further complexes with an organic moiety to form an adduct is shown by Table III.
The Reduced Residue Stick Using Propylene Glycol Adduct of an Antiperspirant
An activated aluminum zirconium glycine propylene glycol salt (available from Reheis, Inc., as Reach AZP-908 PGO) having high density spherical particles with low surface area to mass ratio was formulated into an opaque stick using the formulation shown in Table IV and was compared in blind panel tests versus several well known marketed brands. Twenty-five male and female subjects with varying skin color received a controlled application of products on their forearms, and were then asked to rate the products for residue immediately and thirty minutes after application. The subjective rate scale with a five-point numerical scale with a score of 1 for xe2x80x9cleast residuexe2x80x9d and 5 for xe2x80x9cmost residuexe2x80x9d. Representative results with REACH(copyright) AZP-908 PGO versus national brands are provided in Table IV. The data demonstrates that the reduced residue antiperspirant sticks prepared using polyol containing aluminum zirconium tetrachlorohydrex having high density spherical particles are consistently superior to the control commercial samples tested for perceived residue.
Another benefit derived from the use of these physically modified adducts is improved white color or reduced off white color when the product is viewed in the container. Antiperspirant sticks are more acceptable to consumers if they appear white as opposed to slightly yellowish, since the white color is often associated with quality and purity. Table VI demonstrates improvement in color of the stick when active is replaced by its propylene glycol adduct while using the same base.
When tested at an equivalent active concentration in a suspension roll-on formulation, using volar forearm, propylene glycol adduct of an activated salt showed enhanced efficacy when compared to nonactivated adduct and efficacy equivalent to an activated product. Results are shown by Table VII.
This work established that an inorganicxe2x80x94organic adduct of basic aluminum chlorides and comprising those having the formulas 1, 2 and 3 when formulated into an antiperspirant stick gives significant reduction in white residue and shows significantly reduced color contribution to the stick while maintaining high efficacy.
A primary objective of the present invention is to improve formulations of the hereinabove referenced antiperspirant actives so that practically no white residue is visible even against a black background by the reduction of the particle size, using a refractive index modifier, to a point where the antiperspirant active essentially looses its ability to produce visible interference with the passage of light waves.
One factor which determines the optical appearance of a dispersion formulation is the particle size of antiperspirant and any other ingredients which may be present in the solid form. While the effect of particle size upon optical appearance has been investigated and described in the prior art its practical application in achieving the novel results in accordance with the invention have not been obvious therefrom. The ability of a particle of any given material to scatter or to diffuse light of particular wavelength is a function of its particle size relative to that wavelength. Various estimates have placed the most effective particle diameter for hiding power at approximately one half the wavelength of the light involved. Therefore, as the diameter of a particle becomes increasingly smaller than one half of the shortest wavelength of visible light, about 4000 angstroms for violet, it begins to disappear because it loses its ability to produce visible interference with the passage of light waves.
Since antiperspirant compositions require a very high concentration of active ingredients it has been estimated that the particle sizes to obtain optical clarity need not exceed about 0.20 micron and preferably 0.1 micron. It is also known that dry grinding of antiperspirant to this level is not economically practical or feasible.
Unfortunately, when such small particle sizes are used, other factors become important such as how to prevent such small particles from agglomerating to reform larger particles that could no longer be suited for clear colloidal dispersions.
Individual particles may be associated into agglomerates or aggregates. Particles in an agglomerate are only loosely associated while in an aggregate, the particles are held together strongly to form a ball or block that acts as distinct particles for all practical purposes.
A related problem often encountered in the manufacturing of stick antiperspirant is the settling of an active in the molten stick matrix during the cooling phase resulting in an uneven distribution of the active and hence its uneven performance during the use. To minimize or eliminate this problem, suspending agents such as talc or finely ground silica are used. However, silica and talc present dusting and health related problems and the finished products do not provide excellent skin feel as they tend to increase drag during its application, promote formation of gritty particles and increased residue.
Beside health concerns in handling of silica and talc the product also affects aesthetics of the finished stick; the product tends to have gritiness and leaves moderate white residue on the skin.
It accordingly is an object of this invention to provide an antiperspirant active composition which when formulated into an antiperspirant stick has an improved combination of functional properties, including excellent antiperspirancy, smooth skin feel, nontacky, quick drying and leave no visible residue.
It is another objective of the invention to make antiperspirant compositions which are self suspending and have a long settling time when diluted in antiperspirant formulations such as soft solids, sticks and as a result do not require the use of suspending agents. Such antiperspirant compositions are easier to process and because they omit suspending agents and powder flow enhancers like talc and silica, they avoid health related problems posed by these products from handling in a very fine powder form.
It is another objective of this invention to provide antiperspirant compositions which have an excellent smooth feel during application and have a dry feel after application.
It is a further objective of this invention to provide formulations of excellent antiperpsirancy. The very high surface area of the active results in rapid and efficient delivery of the active to the sweat glands and possible absorption. It is believed that absence or reduced quantity of suspending and flow enhancing agents and gellant and surfactant improves the antiperspirant active""s ability to physically reach the sweat glands and improve efficacy.
Still a further objective of this invention is to provide a cost effective antiperspirant composition that affords the advantages of minimizing capital and processing cost for the antiperspirant and deodorant manufacturers;
The product can be transported within the manufacturing facility readily by a single pumping system for use in antiperspirant sticks, soft solids and other forms in any part of the world as opposed to an expensive pneumatic conveying system for highly hygroscopic finely micronized powder.
The product minimizes inventory and QC/QA cost as the number of ingredients to be stored and assayed are minimized.
The product affords easy technology transfer for a Global Manufacturer and simplifies implementation of uniform product quality between different plants.
It is still another objective of this invention to provide customized ready to use composition for antiperspirant and deodorant manufacturers such that during wet milling other ingredients may be readily incorporated to provide the desirable aesthetics; or enhanced deodorancy by including antimicrobials such as Triclosan, substituted glycerines; like ethyl hexyl glycerine; antioxidants like Vitamin E; fragrance, etc.
The formulations of the invention contemplate those antiperspirants covered by FDA OTC Tentative Final Monograph (Aug. 20, 1982) as Category I.